Optical encoder with variable fiber/phase angle adjustment

Abstract

An optical encoder comprises a sensor head provided with a light emission portion and first and second light reception portions sandwiching the light emission portion therebetween, and a code member on which a plurality of reflective portions are formed at a predetermined pitch, the sensor head being arranged such that the first light reception portion, the light emission portion, and the second light reception portion successively face the code member with respect to the direction of movement of the reflective portions of the code member, and such that an azimuth angle of the light emission and light reception portions with respect to the direction of movement of the reflection portions of the code member can be changed, whereby two output having a predetermined phase difference can be obtained by suitably setting the azimuth angle of the light emission and light reception portions.

I claim: 
     
       1. In an optical encoder having a code member on which a plurality of indicia portions are arranged at a predetermined pitch spacing, means for moving said code member and said indicia portions in one moving direction, and an optical sensor disposed relative to said indicia portions of said code member in order to derive two output signals having a phase difference between them, the improvement wherein said indicia portions are alternating light reflective and non-reflective portions, said sensor comprises a signal head disposed proximate one side of said code member facing said indicia portions and having arranged in a row along a sensor axis a light emission portion between two light reception portions closely adjacent on each side thereof such that light emitted by said light emission portion is reflected by said reflective portions and not reflected by said non-reflective portions and the reflection and non-reflection of light by said alternating portions moving in said moving direction is detected by said two light reception portions to provide two output signals having a phase difference between them,   said light emission and light reception portions being constituted by tip ends of optical fibers arranged in close contact with each other along the sensor axis, and the other ends of the optical fibers being connected to light emission element and light reception elements, respectively, which are remote from the sensor head, and   means for rotating said sensor head in order to adjust an azimuth angle between the sensor axis and the moving direction of the indicia portions of said code member such that a predetermined phase difference between the two output signals is obtained.   
     
     
       2. An optical encoder according to claim 1, wherein said light emission portion has a width along said sensor axis of d separating said light reception portions, said reflective portions have a pitch spacing of p, the azimuth angle is θr, and the phase difference obtained between the two output signals is given by: 360°×(d/p)×cos θr, and is an integer multiple of 90°. 
     
     
       3. An optical encoder according to claim 1, in which said code member includes a rotary disk and said reflective portions are arranged circumferentially on said rotary disk. 
     
     
       4. An optical encoder according to claim 1, in which said code member includes an elongated member and said reflective portions are linearly aligned on the surface of said elongated member.